Following the compelling data obtained in a pivotal phase III clinical trial performed in 218 postmenopausal women suffering from vaginal atrophy who received daily intravaginal 0.25, 0.5 or 1.0% DHEA (dehydroepiandrosterone) ovules for 12 weeks, we have performed analysis of the four co-primary objectives at each site of that multicentre U.S. and Canadian trial. Comparison was made of the change in percentage of parabasal and superficial cells, vaginal pH and severity of the most bothersome symptom. The site-by-site (seven sites) analysis has shown that 10-13 women per group are generally sufficient to obtain a significant or highly statistically significant decrease in vaginal pH and percentage of parabasal cells and increased percentage of superficial cells at p values ranging from 0.02 to <0.0001. For vaginal pain as the most bothersome symptom, a statistically significant difference from baseline was found at six out of seven sites. The exceptionally high consistency between all sites in this phase III study and high potency of the compound permit to obtain a clinically and statistically significant to highly significant effect of treatment on all parameters of vaginal atrophy with the 0.5% DHEA daily intravaginal dose which does not significantly affect the serum levels of oestrogens, thus avoiding systemic risks.